4.20     explain the effects of changes in surface area of a solid, concentration of solutions, pressure of gases and temperature on the rate of a reaction in terms of particle collision theory

Particle Size	Small particle size ⇒ high surface area High surface area ⇒ more collisions per second
Concentration	High concentration ⇒ more particles in a given volume More particles in a given volume ⇒ more collisions per second
Temperature	High temperature ⇒ particles move more quickly (have more kinetic energy) Particles moving more quickly ⇒ more collisions per second Particles also collide with more energy ⇒  more successful collisions.

Exam tip

In explanations, you should always refer to “more collisions per second” or “more frequent collisions”.  Never refer to just “more collisions” or to “greater chance of collision”.